EFFECT OF STORAGE IN GASHOLDER ON ACETYLENE.--It is perfectly true, as has been stated elsewhere, that the gas coming from an acetylene generator loses some of its illuminating power if it is stored over water for any great length of time; such loss being given by Nichols as 94 per cent, in five months, and having been found by one of the authors as 0.63 per cent. per day--figures which stand in fair agreement with one another. This wastage is not due to any decomposition of the acetylene in contact with water, but depends on the various solubilities of the different gases which compose the product obtained from commercial calcium carbide. Inasmuch as an acetylene evolved in the best generator contains some foreign ingredients, and inasmuch as an inferior product contains more (_cf._ Chapter V.), the contents of a holder are never pure; but as those contents are principally made up of acetylene itself, that gas stands at a higher partial pressure in the holder than the impurities. Since acetylene is more soluble in water than any of its diluents or impurities, sulphuretted hydrogen and ammonia excepted, and since the solubility of all gases increases as the pressure at which they are stored rises, the true acetylene in an acetylene holder dissolves in the water more rapidly and comparatively more copiously than the impurities; and thus the acetylene tends to disappear and the impurities to become concentrated within the bell. Simultaneously at the outer part of the seal, air is dissolved in the water; and by processes of diffusion the air so dissolved passes through the liquid from the outside to the inside, where it escapes into the bell, while the dissolved acetylene similarly passes from the inside to the outside of the seal, and there mingles with the atmosphere. Thus, the longer a certain volume of acetylene is stored over water, the more does it become contaminated with the constituents of the atmosphere and with the impurities originally present in it; while as the acetylene is much more soluble than its impurities, more gas escapes from, than enters, the holder by diffusion, and so the bulk of stored gas gradually diminishes. However, the figures previously given show that this action is too slow to be noticeable in practice, for the gas is never stored for more than a few days at a time. The action cannot be accepted as a valid argument against the employment of a holder in acetylene plant. Such deterioration and wastage of gas may be reduced to some extent by the use of a film of some cheap and indifferent oil floating on the water inside an acetylene holder; the economy being caused by the lower solubility of acetylene in oils than in aqueous liquids not saturated with some saline material. Probably almost any oil would answer equally well, provided it was not volatile at the temperature of the holder, and that it did not dry or gum on standing, _e.g._, olive oil or its substitutes; but mineral lubricating oil is